"The truth is, the reality is that schools in the future, if they are faith-based schools, will be able to teach according to their faith and including according to the definition of marriage, according to their faith," Birmingham said.

"That will be respected in the future as it is today. It is patently ridiculous to suggest that allowing same sex couples to marry is somehow going to see some new wave of teaching reforms sweep across the country. That is just not going to happen.

"This is a simple issue and it should not be conflated with other issues."

The controversial ad has also attracted critcism after a Melbourne principal disputed a mother's claim that her son was told he could wear a dress to school.

"The school told my son that he could wear a dress to school next year if he wanted," said Cella White, who has previously appeared in videos attacking the Safe Schools program, in the 30-second commercial.